Motor protective circuit breaker



J. G. JACKSON vMOTOR PROTECTIVE CIRCUIT BREAKER Filed March 9, 1940 Jan. 27; A1942.

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A TTORN E Y Patented Jan. 271942 S PATENT OFFICE 2,271,433 MOTOR PROTECT'IVE CIRCUIT BREAKER John G. Jackson,

Square D Company tion of Michigan Application March 8 Claims.

This invention relatesto electric circuit conntrolling instrumentalities and more particular- 1y to automatic for the protection of motors One object of from overloads.

this invention is to provide an improved form of motor protective device having Aeconomy and simplicity of form.

Another object of this invention is to provide a simplified motor protective device comprising a sealably enclosed automatic electric circuit breaker mechanism and a readily accessible overload protective unit in combination therewith and adapted to eiect automatic operation of the circuit breaker mechanism in response to current overloads of different characteristics than those to which the circuit breaker itself is responsive.

Other objects and features of this invention will be readily apparent to those skilled in the art from the following specification and appended. drawing illustrating certain preferred embodiments of the invention in which:

Figure l is a side elev tion sectional view of the circuit breaker according to the present invention.

Figure 2 is a sectional view taken on the line II--II of Figure 1.

Figure 3 is a sectional view taken on the line III- III of Figure l.

The circuit breaker mechanism illustrated in the drawing follows that shown and described electric circuit breakers adapted` Detroit, Mich., assignor to Detroit, Mich., a corpora- 9, 1940, Serial No. 323,063

' base 6. The legs in PatentfNo. 2,132,623 issued October 11, 1938 to John G. Jackson and Wallace T. Allen. .The particular mechanism used is not material to the invention which lies rather in the combina- 'tion of the protective features.

The motor protective device, according to the present invention, comprises a circuit breaker unit andl an overload protective unit 2 and'is disposed within an enclosing box 3 having a cover 4 mounted thereover, with the cover having an opening therethrough for the passage of the circuit breaker operating handle 5 to the exterior thereof. The circuit breaker unit l, as specifically ends, are pivotally is secured a conducting connector |4 leading to the exterior of the breaker. An insulating sheet l5 separates contact from the connector |4. An arc suppressor I6 and shield |1 are disposed over each of the contacts 9 and Il.

On a bracket I9 rigidly secured to the base 6 adjacent the top thereof is pivotally mounted a carrier I9. Upon this carrier, intermediate its mounted a pair of plates 2| disposed on opposite sides of the carrier. A conducting bar 22 has an integral finger 23 extending from the mid portion thereof which is pivotally supported on the plates 2| by the pivot 24 which also serves to join the plates 2| together for common movement as a unit. The conducting bar 22 has contacts 25 mounted thereon adjacent the ends thereof in position to engage the stationary contacts 9 and The plates 2| are equipped notches 26 in which is located a flipper 21 having parallel legs which are disposed in the notches on opposite sides of the conducting bar 22. The endsrof the flipper legs are joined by a cross bar 28 to which a pair of operating springs with parallel 29 are connected.

A U-shaped operating member 3| is fulcrurned in grooves'32 in the bottom of the cup-shaped of the U are extended at 33 and are joined together by a pin 34 to which the ends of the operating springs 29 are secured.

The carrier,|9 isprovide'd with a surface 35 which is engaged by the pin 34 for resetting the breaker after automatic operations. The carrier is provided at its free end with a latching surface 36 normally engaged by a latch 31 which is pivotally carried by the supporting plate 39 l the bimetal bends shown, comprises an enclosing structure conslsting of 'a base i and a cover 1. The cover 'I is provdedwith a slot 3 through which extends the operating handle 5. The'base 6 in the form of a shallow cu'p in which,.at opposite ends, are disposed stationary contacts 9, Contact 9 is secured to a conducting connector leading to the exterior ofthe enclosure. Contact is rigidly connected to one leg ofr a U-shaped bimetallic member I3 while to the other leg there and is biased toward latching position by spring 39. The latch 31 has a portion thereof provided with an adjustable insulating abutment 4| which is disposed on the low expansion side of the bimetal in a position to be engaged thereby when due to excess current. Openings 42 in the opposite ends of the breaker enclosure are provided for the venting of arc gases. For a more detailed description of the circuit breaker mechanism, reference is made to the aforementioned Patent No. 2,132,623.

The latch 31 is provided with an opening therein through which extends one end of an elongated connecting member 43. The opposite, or right said connecting member 43is threaded and extends through an opening in an end wall of the circuit breaker enclosure to the exterior thereof and is then passed through an opening provided in a bimetallic member 44.

A pin 4I disposed crosswise through the left hand extremity of the connecting member 43 and an latch I1 and the b etallic member 44. With this connective arrangement movement of the bimetallic element 44 to the right will bring about movement o! the latch l1 .in the same direction i9 to swing upwardly under the bias of the operating springs 29 to move the contacts to off position as will hereinafter be described.

An L-shaped conducting element 41 is secured to the connector I4 by a stud 48. A resistor member 43 and the bimetallic element 44 are conductingly secured at their lower extremities to the upwardly directed leg of the L-shaped conducting element 41. Upon the outer ex.. tremity of the conducting element 41 is disposed an insulating block 53 by means of the action of the parts occurs.

In the automatic -operation of the circuit breaker unit itself, upon the occurrence of an overload current thebimetal Il, which is in series with the breaker, becomes heated and bends clockwise moving the latch I1 out of engagement with 'the surface 36, whereupon the carrier I9 swings upwardly under the bias of the operating springs 29 vand the contacts will thus be automatically moved to olf position. To reset the breaker the handle 5 is moved to the right whereupon the pin 34 engages surface Il and moves the latchlng surface I6 into position to be engaged by the latch I1. The parts will then be in normal oil" position and the koperation to on" position will be as previously described.

The bimetallic element i3 of the circuit breaker unit l is factory calibrated and sealed against access and functions to protect the motor and the wiring against short circuits or extremely heavy overloads. However, a motor and which will not injure the wiring but which may be suiilcient, if continued long'enough, to cause injury to the motor. It is for a case such as this that the protective unit comprising the resistor member 4l and the bimetallic member 44 is provided. The resistor and the bimetallic member are so calibrated that the heat generated in the resistor by the current will reachl an c :meeting relation with the amount sumcient to ilex the bimetal 44 member 41 out of engagement with the surface 36 to thereby bring about a breaking of the circuit.

Inasmuch as the device may be used to protect motors in its circuit protective function.

While certain invention have' What is claimed is: 1. An electric circuit breaker `apparatus comprising a sealably enclosed electric circuit break er mechanism having current responsive means for effecting automatic operation thereof upon the occurrence of a current overlo'ad of predeoper-ation of a second current responsive means disposed at the exterior of the enclosed circuit breaker mechanism so as to be readily accessible and comprising a bimetallic element and heater therefor connected in series circuit with the circuit breaker contacts, and means connecting said bimetallic element to said circuit breaker mechanism to effect said circut breaker mechansm t break the circuit when the current through said heater constitutes an overload of, a different predetermined magnitude or duration.

An'electric circuit breaker apparatus comprising a sealably enclosed er mechanism having current responsive means for effecting automatic operation thereof upon the occurrence of a current overload of predetermined mag'n'tude and duration, a second current responsive means disposed at the exterior of the enclosed circuit breaker mechanism so as to be readily accessible and comprising a bimetallic element and heater therefor connected in series circuit with the circuit breaker contacts, and means'connecting said bimetallic element to said circuit breaker mechanism to effect operation of said circuit the circuit when the current through said heater constitutes an overload of a different predetermined magnitude or dur-ation, said connecting means precluding interference tion of said circuit breaker mechanism in response to the action of said first current responsive means.

5. An electric circuit breaker apparatus comprising an electric circuit breaker mechanism having manual means for manual operation and current responsive means forautomatic operation and being sealed within an enclosure against the exterior, a second current responsite means disposed at the exterior of the enclosure in unsealed relation and comprising a.

bimetallic element and a resistance heater with the heater in series circuit with the first current responsive means, and means connecting said bimetallic element and said circuit breaker mechanism to effect operation of said circuit breaker mechanism to break the circuit when the current through said heater exceeds a predetermined current time value relation.

6. An electric circuit breaker apparatus comprising a sealably enclosed electric circuit breaker mechanism having a current responsive means electric circuit breakwith the operaf for effecting automatic operation thereof lwhen the current reaches a predetermined value, said current responsive means comprising bimetallic elements connected in series circuit, a second current responsive means disposed at the exterior of the enclosed circuit breaker mechanism in unsealed relation and comprising a bimetallic element and a resistance heater with the heater also connected in series circuit, and means connecting said bimetallic element and said circuit breaker mechanism to effect operation of said circuit breaker mechanism to break the circuit when the current through said resistor means exceeds a predetermined value for a predetermined period of time.

'1. A motor protective device comprising an enclosure, a self-contained sealably enclosed electric circuit breaker mechanism therein having means responsive to predetermined overload currents of predetermined duration to effect automatic operation of the breaker mechanism to break the circuit therethrough, a second overload means disposed within the enclosure and exteriorly of said sealably enclosed electric circuit in unsealed relation, said second overload means having an operative connection with said circuit breaker mechanism to actuate the mechanism independently of said first overload `.current responsive means and break the circuit when the current exceeds a predetermined value for -a predetermined period of time.

8. A motor protective device comprising an enclosure, a self-contained sealably enclosed electric circuit breaker mechanism therein having tomati'c operation of the break the circuit therethrough, a conducting connector extending from within said sealably enclosed electric circuit breaker mechanism to the exterior thereof, thermal means disposed admechanism and connected to` said conducting connector, said thermal means with the circuit said circuit breaker mechanism independently of said overload current responsive means and break the circuit upon the occurrence of a second predetermined current and time value relation.

' JOHN G. JACKSON.

breaker mechanism to actuate n 

